What to do when you dont understand what is relevant and what is not?

That was never my experience while in school, including law school. All my teachers and profs were more practical-minded and thought in real-world time. I do know that a lot has changed in the education business, and it seems that every school or district is trying some new experiment every year, which leaves the kids as casualties. You will hear that a lot of students these days have little to no critical thinking skills, and that could be your case. Or maybe you just have bad teachers. Talk to the teacher or prof in question and ask for their help, and don't leave until you have a solution that works for you. That's what they're there for.

Well that's education system to you .. we are dumped with all kinda unwanted stuff and nothing relavsnt is available when we need them most.

But try do develop empathy and think afresh. Maybe the examinor wants you to place right arguments and prove your ability to think.